Saatchi launched a tirade of angry words. Four times he grasped her around the neck with Nigella, 53, looking powerless and petrified.

At first he used only his left hand, then both. At one stage he tweaked her nose then pushed both hands in her face. Twice Nigella jerked her head backwards as if in fear.

Several times she nodded ­intently while the conversation became more and more heated.

By the end of the meal she was clearly distraught and in tears.

Now there are fears of severe problems in their 10-year marriage – his third and her second.

Nigella has been abroad ­frequently promoting her latest book and TV series while Saatchi, 70, has become ­ever more reclusive and tetchy.

Jean-Paul

Saatchi leaves the restaurant

The bust-up came after the ­couple had just finished eating at the ­specialist seafood restaurant, a ­popular haunt for ­celebrities ­including Pippa Middleton, Jeremy Clarkson and Simon Cowell.

Nigella and Saatchi always ask for the same table, which is outside ­because he likes to smoke.

It is partly sheltered by olive trees and box bushes. But the attack could be clearly seen and heard by other customers and those passing by the restaurant in the busy street.

Nobody intervened although the incident looked brutal.

A couple on the adjacent table, who briefly chatted with Nigella earlier, turned round and gasped in alarm as they saw her in distress.

She dabbed her eyes on a linen napkin as Saatchi tapped his ­cigarettes impatiently on the table.

Nigella then downed her glass of red wine in one gulp and began to talk, her voice trembling.

She seemed to be trying to pacify her husband, placing a hand on his left wrist as it lay on the table.

At that moment she leaned over and kissed his right cheek.

“It was utterly shocking to watch,” said one onlooker. “I have no doubt she was scared. It was horrific, ­really. She was very tearful and was ­constantly dabbing her eyes.

“Nigella was very, very upset. She had a real look of fear on her face. No man should do that to a woman. She raised her voice and got angry but at the same time was trying to calm him down, almost like you would try to calm down a child.

"The kiss was a strange thing. He was being ­intimidating, ­threatening.

“And yet she kissed him. She ­appeared to be a woman who loves him but was clearly unable to stop him being abusive, ­frightening and ­disrespectful to her.”

Saatchi, 6ft and 17 stone, marched off, leaving his wife sobbing at the table and ­grasping her mobile phone as he got into a car the couple had waiting.

The onlooker said: “He looked guilty. It was clear he knew he’d done something wrong. He was menacing, there’s no ­question. She had been abused and ­humiliated in public.”

As Nigella walked to the car she put a hand to her mouth and bit her lip while wiping away tears.

Jean-Paul

Picture of misery: Nigella flees the scene of the attack

The ­pair returned to the ­£12million converted warehouse in Chelsea, central London, where they live with his daughter Phoebe, 19, and her children Cosima, also 19, and Bruno, 17 – all from ­previous marriages.

Earlier Nigella ­tweeted a ­picture of her ­breakfast – scrambled egg and smoked salmon – without a hint of any trouble at home.

The couple, due to celebrate their 10th ­anniversary in September, went out for lunch last Sunday with Saatchi in his trademark black suit and crisp white shirt.

Nigella wore a black jacket with matching tight leggings and a top with red dots. Earlier this year her ­voluptuous look and sensuous style made her a hit in Hollywood – as a judge on foodie talent show Taste.

Saatchi, who describes himself as a control freak and at times “cringingly vain” has also said his wife’s cookery is wasted on him and he ­prefers ­nursery food such as eggs and beans on toast.

Nigella once said of him: “Charles doesn’t really like proper food. He prefers a bowl of cereal.”

One acquaintance who had a ­conversation with Nigella recently said: “For Saatchi, Nigella has eclipsed him and he’s grumpier.

“His ultimate act of rebellion has been to reject her food. I have a ­feeling that drinking and smoking come into this as well. Her first ­husband John Diamond died of throat cancer in 2001. Yet Saatchi smokes.

“She’d never say anything about it though. She wouldn’t like to do ­anything to upset him.

“Nigella is in awe of him and ­surprisingly lacking in confidence herself. She has been thrilled by the ­reaction she has been getting in America after appearing on TV.

“And with the popularity in Britain it’s boosted her self-esteem.”

A spokesman for Scott’s said last night: “We do not comment on the private matters of customers.”

Neither Nigella nor Saatchi ­responded to requests for a comment when ­asked by the Sunday People.